Methods For Moving A Media Sheet Within An Image Forming Device

ABSTRACT

The present application is directed to methods and devices for determining a media level in an input area within an image forming device. In one embodiment, a support section configured to hold a stack of media sheets is positioned in the image forming device. A pick mechanism is positioned to contact a top-most media sheet of the stack of media sheets in the support section. The pick mechanism may include a pick motor and a pick roller. A sensor roller may be positioned separate from the pick roller and in contact with the top-most media sheet. A controller may determine the media level based on a movement of the sensor roller after the top-most media sheet has moved to a predetermined location.

RELATED APPLICATIONS

The present application is a continuation-in-part of previously filed U.S. patent application Ser. No. 11/406,579 filed on Apr. 19, 2006 and entitled “Methods for Moving a Media Sheet within an Image Forming Device” which is herein incorporated by reference in its entirety.

BACKGROUND

The present application is directed to methods and devices for controlling operation of an image forming device and, more specifically, to methods and devices for determining a media level in arm input area.

Image forming devices, such as a color laser printer facsimile machine, copier, all-in-one device, etc, may include a double transfer system for producing images. Toner is initially transferred from a photoconductive member to an intermediate member at a first transfer location, and then from the intermediate member to the media sheet at a second transfer location. As the toner is being moved towards the second transfer location, a media sheet is moved along a media path to receive the toner image.

The media sheet and toner image should reach the second transfer location at about the same time. If the media sheet arrives before the toner image, the toner image may be transferred to the media sheet at a position that is too low or partially off the bottom of the sheet. Conversely, if the media sheet arrives after the toner image, the toner image may be transferred at a position that is too high or partially off the top of the sheet.

The media path may be configured to allow for increasing and decreasing the speed of the media sheet and thus affect the timing that the media sheet reaches the second transfer location. However, the amount of correction may be limited and large corrections cannot be made. Inherent with this concept is that a shorter media path offers less opportunity for correction. Many image forming devices include short media paths in an effort to reduce the overall size of the device. Therefore, proper timing and media sheet movement is important for these devices as there is limited room for corrections.

SUMMARY

The present application is directed to methods and devices for determining a media level in an input area within an image forming device. In one embodiment, a support section configured to hold a stack of media sheets is positioned in the input area of the image forming device. A pick mechanism is positioned to contact a top-most media sheet of the stack of media sheets in the support section. The pick mechanism may include a pick motor and a pick roller. A sensor roller may be positioned separate from the pick roller and in contact with the top-most media sheet. A controller may determine the media level based on a movement of the sensor roller after the top-most media sheet has moved to a predetermined location.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view illustrating an image forming device according to one embodiment.

FIG. 2 is a perspective view illustrating a sensor according to one embodiment.

FIG. 3 is a schematic view illustrating a pick mechanism, sensor, and a controller according to one embodiment.

FIG. 4 is a perspective view illustrating a sensor according to one embodiment.

FIG. 5 is a schematic view illustrating an image forming device according to one embodiment.

FIG. 6 is a schematic view illustrating a media sheet path according to one embodiment.

FIG. 7 is a process diagram for a control process according to one embodiment.

FIG. 8 is a schematic view of a pick mechanism and a sensor according to one embodiment.

DETAILED DESCRIPTION

The present application is directed to methods and devices for detecting a media level in an input area of an image forming device. The input area may include a support section to contain a stack of media sheets. A pick mechanism may also be located in the input area. The pick mechanism may initiate movement of a top-most media sheet of the media stack. The input area may also include a sensor that may be positioned to also contact the top-most media sheet. The media sheet sensor senses movement of the top-most media sheet as the sheet is moved in response to the pick mechanism. A controller may oversee the operation of the input area. The controller may be configured to determine the media level in the input area by obtaining a feedback from the sensor.

One embodiment of an image forming apparatus is illustrated in FIG. 1. The device 10 includes a support section 11 including a ramp 12 and being sized to contain a stack of media sheets 13. A pick mechanism 20 is positioned at the support section 11 for moving a top-most sheet from the stack 13 along the ramp 12 and into a media path 15. Pick mechanism 20 includes an arm 22 and a roller 21. Arm 22 is pivotally mounted to maintain the roller 21 in contact with the top-most sheet of the stack 13. Pick mechanism 20 may include a clutch 29 that affects the movement of the roller 21. In one specific embodiment, clutch 29 is a ball clutch as disclosed in U.S. patent application Ser. No. 10/436,406 entitled “Pick Mechanism and Algorithm for an Image Forming Apparatus” filed on May 12, 2003, and herein incorporated by reference. A sensor 30 is positioned at the support section 11 to track the movement of the media sheet as will be explained in detail below. The media sheets from the support section 11 are moved along the media path 15 to a second transfer area 40 where they receive a toner image from an image formation area 50.

The image formation area 50 includes a laser printhead 51, one or more image forming units 52, and a transfer member 53. Laser printhead 51 includes a laser that discharges a surface of photoconductive members 54 within each of the image forming units 52. Toner from a toner reservoir is attracted to the surface area affected by the laser printhead 51. In one embodiment, the toner reservoirs (not illustrated) are independent of the image forming units and can be removed and replaced from the device 10 as necessary. In another embodiment, the toner reservoirs are integral with the image forming units 52. In one embodiment, the device 10 includes four separate image forming units 52 each being substantially the same except for the color of the toner. In one embodiment, the device 10 includes image forming units 52 for use with black, magenta, cyan, and yellow toner.

The transfer member 53 extends continuously around a series of rollers 55. The member 53 receives the toner images from each of the photoconductive members 54 and moves the images to the second transfer area 40 where the toner images are transferred to the media sheet. If one embodiment, the toner images from each of the photoconductive members 54 are placed onto the member 53 in an overlapping arrangement. In one embodiment, a multi-color toner image is formed during a single pass of the transfer member 53. By way of example as viewed in FIG. 1, the yellow toner is placed first on the transfer member 53, followed by cyan, magenta, and black.

The second transfer area 40 includes a nip formed by a second transfer roller 41. A media sheet is moved along the media path 15 through the nip and receives the toner images from the transfer member 53. The media sheet with the toner images next moves through a fuser 42 to adhere the toner images to the media sheet. The media sheet is then either discharged into an output tray 43 or moved into a duplex path 45 for forming a toner image on a second side of the media sheet. Examples of the device 10 include Model Nos. C750 and C752, each available from Lexmark International, Inc. of Lexington, Ky., USA. In another embodiment, the device is a mono printer comprising a single image forming unit 42 for forming toner images in a single color. A control panel 44 may be positioned on an exterior surface of an image forming device 10. Commands may be entered through the control panel 44 to control the operation of the image forming device 10. For example, commands to switch modes (e.g., color mode, monochrome mode), view the number of imagers printed, take the device 10 on/off line to perform periodic maintenance, and the like may be entered. The control panel 44 may also include a display panel.

In some embodiments as illustrated in FIG. 1, the time necessary to move a media sheet from the support section 11 to the second transfer area 40 is less than the time to form a toner image on the transfer member 53 and move the toner image to the second transfer area 40. This results in the placement of the toner images on the member 53 before the media sheet is picked from the support section 11. Further, this small distance from the support section 11 to the second transfer area 40 provides little room to correct problems with the timing of the media sheets. Therefore, the media sheets should be picked from the support section 11 in a timely manner and accurately moved along the media path 15.

As illustrated in FIGS. 1 and 2, a sensor 30 is positioned at the support section 11 to determine the position of the media sheet. As best, illustrated in FIG. 2, sensor 30 includes an arm 31 that is pivotally attached to a body of the apparatus 10. A roller 32 is positioned towards an end of the arm 31 and remains in contact with a top-most sheet within the stack 13. A sensor wheel 33 is operatively connected to rotate with the roller 32. The sensor wheel 33 includes a plurality of indicators 34, such as apertures or printed lines, spaced along the circumference of the wheel. In one embodiment, each indicator 34 has a substantially rectangular shape and is positioned around a center of the wheel similar to spokes of a wheel. In one embodiment, each indicator 34 is substantially the same size and evenly spaced from the other indicators 34. In another embodiment, indicators 34 have a plurality of different shapes and sizes, and may be located at different positions along the wheel 33.

A sensor 35 detects rotational movement of the wheel 33. In one embodiment, sensor 35 includes an emitter 36 and a receiver 37. In one embodiment, emitter 36 emits an optical signal that is detected by the receiver 37. As the wheel 33 rotates, the indicators 34 move past the emitter 36 that cause the signal to pass to the receiver 37. Likewise, the other sections of the wheel 33 move past the emitter 36 and prevent the signal from passing to the receiver 37. A controller 100 (FIG. 3) counts the number of pulses and the frequently of the pulses to determine the speed and location of the media sheet.

The emitter 36 may generate any color or intensity of light. The emitter 36 may generate monochromatic and/or coherent light, such as for example, a gas or solid-state laser. Alternatively, the emitter 36 may emit non-coherent light of any color or mix of colors, such as any of a wide variety of visible-fight, infrared or ultraviolet light emitting diodes (LEDs) or incandescent bulbs. In one embodiment, the emitter 36 generates optical energy in the infrared range, and may include an infrared LED. The receiver 37 may comprise any sensor or device operative to detect optical energy emitted by the emitter 36. In one specific embodiment, the emitter 36 is an infrared LED optical emitter and the receiver 37 is a silicon phototransistor optical detector.

FIG. 3 illustrates one embodiment of the input area and media path 15 that leads to the second transfer area 40. The sensor 30 is positioned within the input area to determine the movement of the media sheets from the media stack 13. A second sensor 39 is positioned along the media path 15 between the support section 11 and the second transfer area 40. The second sensor 39 determines the exact position of the media sheet as it moves towards the second transfer area 40. A wide variety of media sensors are, known in the art. In general, the sensor 39 may comprise an electromechanical contact that is made or broken when a media sheet trips a mechanical lever disposed in the media sheet path; an optical sensor whereby a media sheet blocks, attenuates, or reflects optical energy from an optical source, to an optical detector; an opto-mechanical sensor, or other sensor technology, as well known in the art. In one embodiment, the second sensor 39 is positioned about 30 mm upstream from the second transfer area 40.

Controller 100 oversees the timing of the toner images and the media sheets to ensure the two substantially coincide at the second transfer area 40. In one embodiment, controller 100 operates such that the two coincide within +/−0.5 mm. In one embodiment as illustrated in FIG. 3, controller 100 includes a microcontroller with associated memory 101. In one embodiment, controller 100 includes a microprocessor, random access memory, read only memory, and in input/output interface. Controller 100 monitors when the laser printhead 51 begins to place the latent image on the photoconductive members 54, and at what point in time, the first line of the toner image is placed onto the transfer member 53. In one embodiment, controller 100 monitor scan data from the laser printhead 51 and the number of revolutions and rotational position of motor 82 that drive the photoconductive members 54. In one embodiment, a single motor 82 drives each of the photoconductive members 54. In one embodiment, two or more motors 82 drive the plurality of photoconductive members 54. In one embodiment, the number of revolutions and rotational position of motor 82 is ascertained by a sensor 83.

In one embodiment, the controller 100 interfaces with the control panel 44. The control panel 44 may be located on an outer surface of the device 10 to facilitate input of commands to control operation of the device 10. The control panel 44 may also facilitate the input of data stored in memory 101 and further utilized by the controller 100. In one embodiment, the controller 100 uses data stored in memory 101 to determine whether media is present in the support section 11.

In one embodiment, as the first writing line of the toner image is transferred onto the member 53 controller 100 begins to track incrementally the position of the image on member 53 by monitoring the number of revolutions and rotational position of a motor 80 that rotates the member 53. In one embodiment, a sensor 84 ascertains the number of revolutions and rotational position of the motor 80. From the number of rotations and rotational position of the motor 80, the linear movement of member 53 and the image carried thereby can be directly calculated. Since both the location of the toner image on member 53 and the length of member between the transfer nips 59 a, 59 b, 59 c, 59 d and second transfer area 40 is known, the distance remaining for the toner images to travel before reaching the second transfer area 40 can also be calculated.

In one embodiment, the position of the image on the member 53 is determined by HSYNCs that occur when the laser printhead 51 makes a complete scan over one of the photoconductive members 54. Controller 100 monitors the number of HSYNCs and can calculate the position of the image. In one embodiment, one of the colors, such as black, is used as the HSYNC reference for determining timing aspects of image movement. The HSYNCs occur at a known periodic rate and the intermediate member surface speed is assumed to be constant.

At some designated time, pick mechanism 20 receives a command from the controller 100 to pick a media sheet, Motor 81 that drives the pick mechanism 20 is activated and the pick roller 21 begins to rotate and move the media sheet from the stack 13 in the support section 11 into the media path 15. As the media sheet begins to move, the sensor roller 32 and wheel 33 rotate and are detected by the sensor 35. The pick roller 21 continues to rotate and the media sheet moves along the media path 15.

The media sheet moves through the beginning of the media path 15 and eventually trips the media sensor 39. At this point, the controller 100 ascertains the exact location of the leading edge of the media sheet and can incrementally track the continuing position by monitoring the feedback of a sensor 85 associated with pick mechanism motor 81. In one embodiment, because of the short length of the media path 15, pick mechanism 20 moves the media sheet from the support section 11 and into the second transfer area 40. Therefore, the remaining distance from the media sheet to the second transfer area 40 can be calculated from the known distance between the sensor 39 and second transfer area 40 and feedback from the sensor 85. One embodiment of a feedback system is disclosed in U.S. Pat. No. 6,330,424, assigned to Lexmark International, Inc., and herein incorporated by reference.

The media path 15 can be divided into two separate sections: a first section that extends between the support section 11 to a point immediately upstream from the sensor 39; and a second section that extends from the sensor 39 to the second transfer area 40. Sensor 30 provides information to the controller 100 when the media sheet is moving through the first section. Information relating to the second section may be obtained from one or more of the sensor 39, motor 81 and sensor 85.

Controller 100 may use feedback from the sensor 85 to correct variations in the media movement through the first section, Controller 100 may be programmed to assume that activation of the motor 81 results in the media sheet being moved a predetermined amount. However, various factors may result in the media sheet advancing through the first section faster or slower than expected. Some variations are corrected during the first section, and other variations are corrected during the second section. In both corrections, pick mechanism 20 is accelerated or decelerated as necessary.

In some embodiments, the media sheet is not moved as fast as expected causing the media sheet to lag behind the expected location. Causes of a lagging media sheet may include the clutch 29 on the pick roller 21 not engaging, slippage between the pick roller 21 and the media sheet, and wear of the pick roller 21. In each instance, the media sheet is behind the expected location. The amount of lag may be detected based on feed back from the sensor sensor 35. Sensor 35 detects the amount of movement of the media, sheet that is compared by the controller 100 with the expected amount of movement. Any discrepancy, can then be corrected by accelerating the pick mechanism 20 accordingly.

Some variations from the expected position may be corrected in the second section. Examples of these include media stack height uncertainty, and poorly loaded media sheets that are pre-fed up the ramp 12. Because these errors are not caused by the pick mechanism 20, the amount of error is unknown until the leading edge is detected at sensor 39. Once the leading edge is detected, the amount of deviation is determined and the pick mechanism 20 can be accelerated or decelerated as necessary to deliver the media sheet to the second transfer area 40 at the proper time.

Further, feedback from the sensor 39 can be used in combination with the sensor 35 for feeding future media sheets. By way of example, the height of the media stack 13 is unknown when feeding a first sheet. The controller 100 may estimate an expected travel time and activate the pick mechanism 20 at a corresponding time. Once the leading edge reaches the sensor 39, the feedback from the sensor 35 can be used to determine the distance the sheet traveled from the stack 13 to the sensor 39 to determine the height of the media stack 13. With this information, controller 100 is able to more accurately predict future pick timings. More specific embodiments for determining the media level within the support section 11 are described below.

FIG. 4 illustrates another embodiment of the sensor 30. Roller 32 is rotatably mounted on an arm 31. The roller 32 includes a plurality of indicators 34 that move past a sensor 35. The sensor 35 includes an emitter (not illustrated) and a receiver 37. The roller 32 is maintained in contact with the top-most sheet of the media stack 13 as the arm 31 pivots about a point 89. Movement of the top-most media sheet causes the roller 32 to rotate which is detected by the sensor 35.

It should be noted that the image-forming device 10 illustrated in the previous embodiments is a two-stage image-forming apparatus. In two-stage transfer apparatus, the toner image is first transferred to a moving transport member 53, such as an endless belt, and then to a print media at the second transfer area 40. However, the present devices and methods are not so limited, and may be employed in single-stage or direct transfer image-forming device 80, such as the image-forming device, shown in FIG. 5.

In such a device 80, the pick mechanism 20 picks an upper most print media from the media stack 13, and feeds it into the primary paper path 15. Sensor 30 is positioned at the input area and includes an arm 31 including a roller 32 and sensor wheel 33. The roller 32 is positioned on the topmost sheet and movement of the sheet causes the sensor wheel 33 to rotate which is then detected by sensor 35. In one embodiment, media rollers 16 are positioned between the pick mechanism 20 and the first image forming station 52. The media rollers 16 move the media sheet further along the media path 15 towards the image forming stations 52, and may further align the sheet and more accurately control the movement. It one embodiment, the rollers 16 are positioned in proximity to the input area such that the media sheet remains in contact with the sensor 30 as the leading edge moves through the rollers 16. In this embodiment, sensor 30 may monitor the location and movement of the media sheet which can then be used by the controller 100. In another embodiment, the media sheet has moved beyond the sensor 30 prior to the leading edge reaching the rollers 16.

The image forming device 80 may also include a multipurpose feeder 60 that may be configured to allow feeding of media such as envelopes, post cards, transparencies, or card stock, as well as media that may be too large to fit in the support section 11. The multipurpose feeder 60 may also be used to manually feed media. A pick mechanism 61 picks a top-most media sheet from a media stack 70 in a support section 68 and feeds it into the media path 15. A media sheet sensor 63 is positioned in the input area and includes an arm 64 including a sensor roller 65 and a sensor wheel 66. The sensor roller 65 is positioned to contact the top-most media sheet of the media stack 70. Movement of the media sheet causes the sensor roller 65 to rotate which is then detected by a sensor 67. In one embodiment, media rollers 16 are positioned between the pick mechanism 61 and a first image forming station 52. The media rollers 16 move the media sheet further along the media path 15 towards the image forming stations 52, and may further align the sheet and more accurately control the movement. In one embodiment, the rollers 16 are positioned in proximity to the input area such that the media sheet remains in contact. With the media sheet sensor 63 as the leading edge moves through the rollers 16. In this embodiment, media sheet sensor 63 monitors the location and movement of the media sheet which can then be used by the controller 100. In another embodiment, the media sheet has moved beyond the media sheet sensor 63 prior to the leading edge reaching the rollers 16.

The transport member 53 conveys the media sheet past each image-forming station 52. Toner images from the image forming stations 20 are directly transferred to the media sheet. The transport member 53 continues to convey the print media with toner images thereon to the fuser 42. The media sheet is then either discharged into the output tray 43, or moved into the duplex path 45 for forming a toner image on a second side of the print media.

In one embodiment, the roller 21 of the pick mechanism 20 is mounted on a first, arm 22, and the sensor roller 32 is mounted on a second arm 31. In one embodiment, the pick roller 21 is positioned downstream of the sensor roller 32.

The sensor 30 may further be able to detect the trailing edge of the media sheet as it leaves the media stack 13. As the media sheet is moved from the stack 135 the sensor 30 senses the sheet until the trailing edge moves beyond the roller 32. At this point, the roller 32 stops rotating and a signal may be sent to the controller 100 indicating that the location of the trailing edge. The controller 100 may then begin picking the next media sheet based on the known location of the trailing edge. By knowing this location, the controller 100 does not need to wait for a minimum gap to be formed between the trailing edge and the next sheet. The next sheet may then be picked once the trailing edge is clear and the pick mechanism 20 is ready to pick the next media sheet from the stack 13.

Early picking of a media sheet may have several advantages. First, picking the next media sheet early allows the pick mechanism 20 to tolerate slippage between the pick roller 21 and media sheet, and clutch errors. Second, the staging system may be, able to tolerate more error when the media sheet is early because it can eliminate more error by decelerating than by accelerating. Third, if no media sheet movement is detected by the sensor 35, the controller 100 can stop the pick mechanism 20 and reinitiate the pick. Reinitiating may occur prior to the error becoming so large that the staging zones could not remove the error.

In one embodiment, pick mechanism 20 moves the media sheet from the support section 11 (e.g., an input tray) and into the second transfer area 40. As the media level in the support section 11 changes, the length of the path from a leading edge of the top-most media sheet at the ramp 12 to the media position sensor 39 also changes. This is illustrated in FIG. 6 where D is the distance from the leading edge of the top-most media sheet (Point B) to the media position sensor 39 when the support section 11 is full, and D₂, is the distance from the leading edge of the top-most media sheet to the media position sensor 39 when the support section 11 is nearly empty. When the pick roller 21 moves the top-most media sheet, the sheet may follow a path approximated by A-B′-C. The length of this path may continually increase as the media level decreases and each successive sheet that is fed from the support section 11 may have a longer distance to travel before encountering the media position sensor 39. Therefore, the amount of movement of the sensor roller 32 increases as the media level in the support section 1 decreases. Experimentation has shown that the media level can be estimated through an empirical relationship between the amount of movement of the sensor roller 32 and the angle α that the ramp 12 is disposed from vertical.

One or more parameters may be measured to quantify the movement of the sensor roller 32. For example, empirical testing has been performed to measure the correlation between a distance the top-most media sheet travels when picked by the pick roller 21 and each rotation of the sensor roller 32. A similar correlation may be made with an amount of time the sensor roller 32 rotates.

The one or more parameters used to quantify the movement of the sensor roller 32 may be programmed into the controller 100 when the image forming device 10 is initially built. In another embodiment, the parameters are stored in the memory 101. Over a period of time, the values of the parameters may change. For example, as the sensor roller 32 wears, the correlation between rotation of the sensor roller 32 and the distance traveled by the top-most media sheet may change. Therefore, it may be desirable to input new values for the parameters. In one embodiment, the new values are entered into the controller 100 or the memory 101 through the control panel 44. In another embodiment, controller 100 maintains ongoing values that are, periodically updated.

In one embodiment, the controller 400 controls the input area according to a process 600 shown in FIG. 7. The controller 100 sends a signal to the pick motor 81 to begin rotating (block 605). The pick motor 81 rotates the pick roller 21. The pick roller 21 then moves the top-most media sheet from the media stack 13. The movement of the top-most media sheet drives movement of the sensor roller 325 which is detected by the sensor detector 35. A signal is sent from the sensor detector to the controller 100. The controller 100 then keeps track of the amount of movement of the sensor roller 32 (block 610). The pick roller 21 continues to advance the media sheet towards the media position sensor 39 (block 620). When the media position sensor 39 is triggered, indicating that the leading edge of the media sheet has reached the media position sensor 39 (block 615) the controller 100 ascertains the total movement of the sensor roller 32 (block 625). The controller 100 then determines the media level based on the total movement of the sensor roller 32 (block 630). The controller 100 may then generate a display on the control panel 44 indicating the media level (block 635). The display may, for example, be a graphic or numeric representation of the media level.

The above describes methods and devices that rely on the media sheet sensor 30, 63 positioned relative to the pick mechanism 20, 61 on an opposite side of the pick mechanism pivot, as shown in FIGS. 1, 3, and 5. In other embodiments, however, the media sheet sensor 30, 63 may have a different orientation relative to the pick mechanism pivot. In one embodiment, the media sheet sensor 30, 63 may be positioned on the same side of the pick mechanism pivot, as shown in FIG. 8.

Spatially relative terms such as “under”, “below”, “lower”, “over”, “upper”, and the like, are used for ease of description to explain the positioning of one element relative to a second element. These terms are intended to encompass different orientations of the device in addition to different orientations than those depicted in the figures. Further, terms such as “first”, “second”, and the like, are also used to describe various elements, regions, sections, etc and are also not intended to be limiting, Like terms refer to like elements throughout the description.

As used herein, the terms “having”, “containing”, “including”, “comprising” and the like are open ended terms that indicate the presence of stated elements or features, but do not preclude additional elements or features. The articles “a”, “an” and “the” are intended to include the plural as well as the singular, unless the context clearly indicates otherwise.

The present devices and methods may be carried out in other specific ways than those herein set forth without departing from the scope and essential characteristics. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein. 

1. A device to determine a media level within an image forming devices the device comprising: a pick mechanism to feed media sheets from a stack of media sheets; a sensor roller to contact a top-most media sheet of the media stack, the sensor roller rotates when the top-most media sheet is being fed by the pick mechanism; a media position sensor located downstream from the sensor roller; and a controller configured to determine the media level based on movement of the sensor roller and a time for the top-most media sheet to move from the media stack to the media position sensor.
 2. The device of claim 1, wherein the controller is configured to determine the media level based on a difference between when the top-most media sheet is picked by the pick roller and when the top-most media sheet is sensed by the media position sensor.
 3. The device of claim 1, wherein the controller is configured to determine the media level based on a time from when a pick mechanism begins to move the top-most media sheet from the media stack until the top-most media sheet is sensed by the media position sensor.
 4. The device of claim 1, wherein the pick mechanism is configured to move the top-most media sheet from the media stack to the media position sensor.
 5. The device of claim 1, wherein the pick mechanism further comprises a pick roller positioned to contact the top-most media sheet of the media stack, wherein the pick roller and sensor roller are spaced apart and simultaneously contact the top-most media sheet while the media sheet is being fed.
 6. The device of claim 5, wherein the pick roller and the sensor roller are each positioned at an input tray.
 7. The device of claim 5, wherein the pick roller is mounted on a first arm and the sensor roller is mounted on a second arm.
 8. A device to determine a media level within an image forming device, the device comprising: a sensor roller positioned to contact a top-most media sheet of a stack of media sheets, the sensor roller being rotated when the top-most media sheet moves from the media stack; a media position sensor located downstream from the sensor roller; and a controller configured to determine the media level based on movement of the sensor roller and a time for the top-most media sheet to move from the media stack to the media position sensor.
 9. The device of claim 8, further comprising a pick mechanism to contact and drive the top-most media sheet from the media stack.
 10. The device of claim 8, wherein the sensor roller further includes a plurality of indicators that are sensed by a sensor during rotation of the sensor roller.
 11. The device of claim 8, further comprising a sensor wheel positioned adjacent to the sensor roller, the sensor wheel including a plurality of indicators that are sensed by a sensor during rotation of the sensor roller.
 12. The device of claim 9, wherein the pick mechanism is mounted on a first arm and the sensor roller is mounted on a second arm.
 13. The device of claim 9, wherein the pick mechanism and the sensor roller simultaneously contact the top-most media sheet while the media sheet is being fed.
 14. A method of determining a media level within an image forming device, the method comprising the steps of: sending a signal to begin rotating a pick roller that is in contact with a top-most media sheet in a stack of media sheets; receiving feedback from a sensor roller also in contact with the top-most media sheet indicating movement of the top-most media sheet; receiving a signal from a media position sensor that the top-most media sheet is at a predetermined position downstream from the media stack; and determining the media level based on movement of the sensor roller and receiving the signal from the media position sensor.
 15. The method of claim 14, wherein the step of receiving a feedback from the sensor roller in contact with the top-most media sheet further comprises sensing indicators on the sensor roller that move past a sensor during rotation of the sensor roller.
 16. The method of claim 14, wherein the step of receiving a feedback from a sensor roller in contact with the topmost media sheet further comprises sensing indicators on a sensor wheel positioned adjacent to the sensor roller, the indicators moving past a sensor during rotation of the sensor roller.
 17. The method of claim 14, wherein the step of determining the media level based on movement of the sensor roller comprises determining the number of rotations of the sensor roller between sending the signal to the pick roller to begin rotating and receiving the signal from the media position sensor.
 18. The method of claim 14, wherein the step of determining the media level based on movement of the sensor roller comprises determining the time of rotation of the sensor roller between sending the signal to the pick roller to begin rotating and receiving the signal from the media position sensor.
 19. The method of claim 14, wherein the step of receiving a feedback from a sensor roller in contact with the top-most media sheet further comprises driving the sensor roller to rotate by moving the top-most media sheet from the media stack.
 20. The method of claim 14, wherein the step of determining the media level further comprises displaying the media level on a control panel of the image forming device. 